Method and arrangement for generating a laser beam having a differing beam profile characteristic by means of a multi-clad fiber

Abstract

The invention concerns a method for generating a laser beam ( 3 ) with different beam profile characteristics, whereby a laser beam ( 2 ) is coupled into one fiber end ( 1 a ) of a multi-clad fiber ( 1 ), in particular a double-clad fiber, and emitted from the other fiber end ( 1 b ) of the multi-clad fiber ( 1 ) and whereby, to generate different beam profile characteristics of the output laser beam ( 3 ), the input laser beam ( 2 ) is electively coupled either at least into the inner fiber core ( 4 ) of the multi-clad fiber ( 1 ) or at least into at least one outer ring core ( 6 ) of the multi-clad fiber ( 1 ), as well as a corresponding arrangement ( 10 ).

What is claimed is: 
     
       1. A method for generating a laser beam ( 3 ) with different beam profile characteristics,
 characterised in that: 
 a laser beam ( 2 ;  61 ,  62 ) is coupled into the fibre end ( 1   a ) of a multi-clad fibre ( 1 ), in particular a double-clad fibre, and emitted from the other fibre end ( 1   b ) of the multi-clad fibre ( 1 ), and 
 for the generation of different beam profile characteristics of the output laser beam ( 3 ), either the input laser beam ( 2 ;  61 ,  62 ) is electively either coupled at least into the inner fibre core ( 4 ) of the multi-clad fibre ( 1 ) or at least into at least one outer ring core ( 6 ) of the multi-clad fibre ( 1 ) or, electively, a first laser beam ( 61 ) is coupled at least into the inner fibre core ( 4 ) of the multi-clad fibre ( 1 ) and a different, second laser beam ( 62 ) is coupled at least into at least one outer ring core ( 6 ) of the multi-clad fibre ( 1 ). 
 
     
     
       2. A method according to  claim 1 , characterised in that, for electively coupling of the laser beam ( 2 ) into the multi-clad fibre ( 1 ), relative motion takes place between the input laser beam ( 2 ) and the coupling-side face ( 8 ) of the multi-clad fibre ( 1 ) in a direction ( 12 ) transverse to the laser beam ( 2 ). 
     
     
       3. A method according to  claim 1 , characterised in that, for electively coupling of the laser beam ( 2 ) into the multi-clad fibre ( 1 ), the input laser beam ( 2 ) with respectively different beam cross-sections, in particular with respectively different beam diameters, is projected onto the coupling-side face ( 8 ) of the multi-clad fibre ( 1 ). 
     
     
       4. A method according to  claim 1 , characterised in that, for the coupling of the laser beam ( 2 ) into both the inner fibre core ( 4 ) and at least one outer ring core ( 6 ), the input laser beam ( 2 ) is divided into at least two sub-beams ( 2   a ,  2   b ), each of which is coupled into one of the cores ( 4 ,  6 ) of the multi-clad fibre ( 1 ). 
     
     
       5. An arrangement ( 10 ;  20 ;  30 ;  60 ) for generating a laser beam ( 3 ) with different beam profile characteristics,
 characterised by: 
 a multi-clad fibre ( 1 ), in particular a double-clad fibre with one inner fibre core ( 4 ) and at least one outer ring core ( 6 ), and 
 a switchable device ( 11 ,  13 ;  21 ,  22 ;  23 ;  31 ,  32 ;  65 ) with at least two switch positions in which an input laser beam ( 2 ;  61 ,  62 ) is electively coupled either at least into the inner fibre core ( 4 ) of the multi-clad fibre ( 1 ) or at least into at least one outer ring core ( 6 ) of the multi-clad fibre ( 1 ) or, electively, a first laser beam ( 61 ) is coupled at least into the inner fibre core ( 4 ) of the multi-clad fibre ( 1 ) and a different, second laser beam ( 62 ) is coupled at least into at least one outer ring core ( 6 ) of the multi-clad fibre ( 1 ). 
 
     
     
       6. An arrangement according to  claim 5 , characterised in that the switchable device comprises adjustable deflection optics ( 11 ,  22 ,  31 ,  32 ) which, in their at least two switch positions, deflect an input laser beam ( 2 ) in a direction ( 12 ) transverse to the axis of the coupling-side face ( 8 ) to varying extents and/or a control device ( 13 ) which, in its at least two switch positions, moves the coupling-side face ( 8 ) of the multi-clad fibre ( 1 ) in a direction ( 12 ) transverse to the input laser beam ( 2 ) to varying extents. 
     
     
       7. An arrangement according to  claim 6 , characterised in that the deflection optics comprises an optical element ( 22 ,  31 ,  32 ) which can be positioned in at least two different switch positions transverse to the laser axis. 
     
     
       8. An arrangement according to  claim 5 , characterised in that the switchable device comprises adjustable optics ( 21 ;  23 ) or an adjustable aperture which, in their at least two switch positions, project the input laser beam ( 2 ) with different beam cross-sections, in particular with different beam diameters, onto the coupling-side face ( 8 ) of the double-clad fibre ( 1 ). 
     
     
       9. An arrangement according to  claim 8 , characterised in that the adjustable optics ( 23 ) can be moved back and forth along the laser beam axis between their at least two switch positions. 
     
     
       10. An arrangement according to  claim 7 , characterised in that the optical element ( 31 ) or an aperture is arranged in one switch position outside the beam path of the laser beam ( 2 ) and in at least one other switch position at least partially in the beam path of the laser beam ( 2 ). 
     
     
       11. An arrangement according to  claim 10 , characterised in that the optical element is formed by a beam divider, in particular an optical wedge plate ( 31 ), which can be moved into the laser beam ( 2 ), to divide the input laser beam ( 2 ) into at least two sub-beams ( 2   a ,  2   b ) each of which is coupled into one of the cores ( 4 ,  6 ) of the multi-clad fibre ( 1 ). 
     
     
       12. An arrangement according to  claim 5 , characterised in that the diameter ( 2  r 1 ) of the inner fibre core ( 4 ) of the multi-clad fibre ( 1 ) is maximum approximately 200 μm, in particular maximum approximately 150 μm and preferably maximum approximately 120 μm. 
     
     
       13. An arrangement according to  claim 5 , characterised in that the ring thickness (r 3 -r 2 ) of the at least one outer ring core ( 6 ) of the multi-clad fibre ( 1 ) is greater than or equal to the diameter ( 2  r 1 ) of the inner fibre core ( 4 ). 
     
     
       14. An arrangement according to  claim 5 , characterised in that, for the multi-clad fibre ( 1 ), the numerical aperture of a first cladding ( 5 ) surrounding the inner fibre core ( 4 ) is higher than the numerical aperture of a second cladding ( 7 ) surrounding the at least one outer ring core ( 6 ). 
     
     
       15. An arrangement according to  claim 5 , characterised in that the switchable device ( 65 ) comprises, on the input side, two optical fibres ( 63 ,  64 ) via which two different laser beams ( 61 ,  62 ) can be supplied, whereby the switchable device ( 65 ) electively couples one laser beam ( 61 ) at least into the inner fibre core ( 4 ) of the multi-clad fibre ( 1 ) and the other laser beam ( 62 ) at least into at least one outer ring core ( 6 ) of the multi-clad fibre ( 1 ).